Caddy Main Bearing Studs

[one finger john]

In an other forum, the Op had said that he had torqued his main studs "20 to 30" times for engine mock up purposes. The studs were looking raggedy and worn. I made the comment that he was wearing out his fasteners before the engine had even been fired. He took offense.

My question is... how many times can a quality stud (ARP, Donovan, etc. ) be torqued to its' designed stretch limit (in this case 95 lbs, Caddy 500 main stud, didn't say who made the unknown stud) before it is deemed ready for replacement?

Same engine has rod cap bolts (not nuts). After how many torque cycles should they be replaced?

Hope I can get Mike's input on this.

TIA, John

 

[Dino]

I'm not Mike but i was told no more then 3 times before replacing them. That what we did on dirt race car motor.

 

[WMG]

Depending on the application, hard use etc., twice but never more than three times. You do not want them to fail because of what is a realatively minor expense in a rebuild.

 

[Francis Blake]

Why torque them down for mock up purposes?

 

[Screaming Metal]

http://www.enginebuildermag.com/Article/105791/ten_head_bolt_installation_tips.aspx

 

[Screaming Metal]

Why torque them down for mock up purposes?

For machining of Splayed Caps, custom main cap milling (angle milling). On the head deck surfaces, especially when doing all sorts of funky work on the manifold faces.

You mic your fasteners, once its beyond a certain point, that fastener has been compromised. this also goes for the threaded holes in the blocks.

 

[Wild Mango]

http://www.enginebuildermag.com/Article/105791/ten_head_bolt_installation_tips.aspx

Engine Builder Magazine, always good. Every issue, I learn something and learning stuff is good, even for old dogs.................
If you think of a fastener as a tension spring, which it is. If you torque it below its elastic limit it should return to original length when you relieve the torque. People like ARP set torque values for a particular fastener below the elastic limit to ensure reliability. Do what they say. As Screamin' says, fatigue lowers elastic limits, and your first clue you have exceeded elastic limit is that the fastener does not return to original length when unloaded. Thats why any engine builder worth his salt ration always measures used rod bolts and any that remain elongated by even a fraction are ruthlessly purged. I tend to discard the whole lot, I'rather spring for new bolts at $100:00 than cop $300:00 for an oildown and then shovel the remains into bins to take home. Ditto for head studs or bolts, cheap insurance to buy new. (valve retainers, collets and springs too, for that matter)
Torque To Limit fasteners, they are one time only. Period. One time, thats it and get them in the gash bin before one sneaks back into the build room.